Memantine (1-amino-3,5-dimethyl adamantane), its therapeutic use and methods for its preparation are known in the art. For a summary of the prior art in this respect reference is made to U.S. provisional application 61/062,602 and EP 08001545.6.
International Publication No. WO 2006/122238 discloses processes for preparing memantine or an acid addition salt of memantine, which involve either reaction of 1-bromo-3,5-dimethyladamantane with formamide to form N-formyl-1-amino-3,5-dimethyladamantane or reaction of 1-hydroxy-3,5-dimethyladamantane with a hydrogen halide to obtain 1-halo-3,5-dimethyl adamantane which is then reacted with formamide to yield N-formyl-1-amino-3,5-dimethyladamantane. The N-formyl-1-amino-3,5-dimethyladamantane intermediate is deformylated under acidic conditions to yield memantine hydrochloride. Excess of bromine is distilled off from the reaction mass, after the reaction is completed. The reactions disclosed therein are summarized in the following scheme 1:

LV 1318613 B relates to a method of preparation of 1-amino-3,5-dimethyladamantane hydrochloride (memantine HCl) wherein 1,3-dimethyladamantane is reacted with nitric acid followed by addition of urea and heating of the reaction mixture. Nitric acid is added at 10-30° C. to the pre-formed emulsion of the hydrocarbon in acetic acid and subsequently, 30-55% of aqueous urea solution is added in the molar ratio 1,3-dimethyladamantane-acetic acid-urea 1:3-4:9-12:2.5-5-0 accordingly.
Kisilenko et al. (“Bromine complexes of 1-bromoadamantanes”, Translation from Zhurnal Obshchei Khimii, vol. 57, No. 12, pg. 2659-2662, Plenum publishing corporation, pages 2370-2372, 1988) have shown that 1-bromoadamantanes form fairly stable complexes with bromine.
The Russian patent application RU 2 309 940 discloses a method for the preparation of 3,5-dimethyladamantyl-1-amine or its salts. The method includes a stage of bromination of 1,3-dimethyladamantane with liquid bromine while boiling. Bromination is carried out with a molar ratio of 1,3-dimethyladamantane to bromine of 1 to 2 to 8, or 1 to 3 to 6, and the bromine is separated off by distillation. When using the claimed method, the yield of the target product is 63 to 75%. DIKTAT MR
WO 2008/062472 also relates to a process for preparing memantine or an acid addition salt of memantine comprising the reaction of 1-bromo-3,5-dimethyladamantane with formamide to form 1-N-formyl-3,5-dimethyl adamantane.